It is given to you by a fisherman on Dewford.
With the old rod you have the lovely selections of Magikarp and Tentacool
I suggest you get a rod (Old rod, good rod, super rod) or find HM03 (Surf).
No you find it in Pokemon mansion.
It is at vermilion city.
You can find the Old Rod, or as you called it the Normal Rod, towards the left of Jubilife City.
The old rod is given to you in Dewford Town by a fisherman on the east side of the gym.
You find old rod at dewford town You find Good rod at route 118 You find Super rod At Mossdeep town in a building. (Hardest to find)
you can find the old rod on route 32 or you can find the good rod in olivine city
you use a old rod anywhere
anywhere using an old rod.
Using the Old Rod in Pokemon Ruby (or any Pokemon game for that matter) will get you a Magikarp as that is the only Pokemon an Old Rod can catch.
The Old Rod is unobtainable in Pokemon Black and White.